And Sturridge. However I think it more likely we won't directly replace Coutinho but bring in a striker (Aubameyang ?) to replace Studge. That still leaves us with a very powerful forward line (Mane, Salah, Firmino, Lallana, Auba ?). I would disagree with a 5+1 assessment of what is needed. A stronger midfield would greatly improve the defence too. So a high quality partner for Keita and VVD or a.n.other high quality CB would instantly transform the team. That's only 2 players (since Keita is already done). Of course another 1 or 2 1st team quality players wouldn't hinder but we are a long way from 5+1.
Coutinho will leave - That will need a replacement.
We desperately need a holding midfielder.
Desperately need a centreback.
That's 3 that are absolutely needed. Beyond that in the region between necessary and nice to have:
a proper goalkeeper (I am still on wait and see with karius)
A striker to replace sturridge
another centreback
so 3-6 signings. 4 of them done by the end of this summer would constitute a competent performance in the transfer market (though we should be looking at 5). I am not holding my breath though. all 6 would be the stuff of miracles by FSG standards.